Chemiluminescence air pollutants monitoring device

ABSTRACT

Device or apparatus for chemiluminescence air pollutants monitoring including a plurality of microreactors simultaneously active to receive ambient air and reagents, monitoring of the microreactors being accomplished sequentially by a single photomultiplier and wherein channel monitoring is controlled by a rotary shutter which moves discretely from microreactor to microreactor, the microreactors consisting of channels. A quantitative analysis of gaseous components of the atmosphere is obtained by comparison of the signals obtained from the separate channels with appropriate calibration standards and processing circuitry.

0 I, a a United States atem [151 3,700,896

Anderson et al. 5] Oct. 24, 1972 CHEMILUMINESCENCE AIR [56] ReferencesCited POLLUTANTS MONITORING DEVICE UNITED STATES PATENTS [72] Inventors:Howard H. Anderson, Covina; Ru-

dolph M w Covina; 3,271,113 9/1966 Van Pul ..250/71 R Donald J, Sibb C mg 3,574,064 4/1971 Binnings et al ..250/7l R David C. Sutherland, ElMonte, all of Calif. Primary Examiner-Archie R. Borchelt 73 Assignee:Geomet, Incorporated, Rockville, Mama-Dav Semmes 57 ABSTRACT [22] Filed:Sept. 10, 1970 l f h l n evice or apparatus or c emi ummescence air pou- [211 App! 7l057 tants monitoring including a plurality ofmicroreactors Related Applicafion Data simultaneously active to receiveambient air and re- 63 C f S N 63 844 A agents, monitoring of themicroreactors being accom- 1 z igya g g g gb plished sequentially by asingle photomultiplier and wherein channel monitoring is controlled by arotary [52] U 5 Cl 250/71 R 23/254 E 250/71 5 R shutter which movesdiscretely from microreactor to [51] n 'Gol zilsz microreactor, themicroreactors consisting of chan- [58] Field of seal-Z51: III/2 567713%,"l if R, 83.3 IR, nels- A quamitafive analysis gamus the atmosphere isobtained by comparison of the signals obtained from the separatechannels with appropriate calibration standards and processingcircuitry.

17 Claims, 7 Drawing Figures [0 AMBIENT AIR MANIFOLD /|6 H2 02 Fe 304RESERVOIR COLUMN ,4 36 O PHOTOMULTI PLIER FACE I8 (2 IN. DIAMETER)LUM|N0LN0OH RESERVOIR FROM CELL EXHAUSTS LIQUID AIR m VACUUM SEPARATORPUMP PAIENTED B 24 I972 3 700 896 saw 2 0F 4 FIG. 2

sum 3 or 4 PATENTED um 24 I972 FIG.

(FILTERED AIR) STA.1

CHEMILUMINESCENCE AIR POLLUTANT S MONITORING DEVICE CROSS-REFERENCES TORELATED APPLICATIONS This application is a continuation-in-part of ourcopending application entitled A SYSTEM AND METHOD OF AIR POLLUTIONMONITORING UTILIZING CHEMILUMINESCENCE REACTIONS, Serial No. 63,844,filed Aug. 14, 1970, now US. Pat. No. 3,659,100.

SUMMARY OF THE INVENTION The present invention is for a device orapparatus used in automatic chemiluminescence air monitoring wherein asingle photomultiplier is operable as a sensor for five or six reactorcells or channels. The invention teaches a simple form ofinstrumentation for applying a luminol-chemiluminescence technology tosolving problems associated with obtaining an analysis of pollutantgases in the ambient atmosphere. A system and method are described inour aforesaid co-pending patent application. The present invention isdirected more specifically to the mechanical aspects of the test cellassembly and associated mechanisms.

The apparatus of the invention is useful in the system and method whichbasically consists of an air supply fed via a manifold through limitingorifices into five or six small diameter U-tube cells. At the entry toeach cell, the small quantity of luminol-hydrogen peroxide solutions areadded to the air stream. The heterogeneous system (air-liquid) flowsthrough the cells to a liquid gas separator (drop-out pot) and thence towaste. The sensor signal, in terms of light output, occurs at thesurface of the gas-liquid interface in the cells. The sampled air passesthrough the vacuum pump while the liquid may be bled off from theseparator or continuously removed. The ambient air streams passing tothe cells are processed in absorption columns in order to separate thegaseous components which are measured.

The multiple cell including a plurality of separate channels is usableselectively by means of ashutter mechanism for sequentially monitoringeach of the channels, the rotary shutter moving discretely from channelto channel.

Additional features, advantages and objects of the invention will bemore readily apparent from the following detailed description of anembodiment thereof when taken together with the accompanying drawing inwhich:

FIG. 1 is a schematic diagram of an automatic chemiluminescence airmonitor in accordance with the invention indicating air and liquid flowpaths;

FIG. 2 is a view of the cell assembly for use in practicing theinvention as set up for five test channels, a portion being broken awayfor clarity of detail;

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 2;

FIG. 5 is a schematic view of a filter holder and retainer for in-lineuse;

FIG. 6 is a sectional view of a filter retainer corresponding with FIG.5; and

FIG. 7 is a schematic of a control and operating circuit for theinvention.

Referring now more specifically to the drawings a concept of the broadprinciples of the invention is apparent from the schematic diagram ofthe monitor in FIG. 1 showing the various air and liquid flow paths. Theair supply is fed via an ambient air manifold generally indicated at 10through limiting orifices generally designated 12 into a plurality of,in the present instance five, preferably one quarter in. diameter (I.D.)or smaller, U-tube cells indicated at 14. At the entry to each cell, asmall quantity (0.1 ml/min) of luminol-hydrogen peroxide solutions fromreservoirs l6 and 18 thereof respectively are added to the air stream.The heterogeneous system (air-liquid) flows through the cells to aliquid gas separator 20 in the nature of a drop-out pot and thence towaste as indicated at 22. A desired sensor signal, in terms of lightoutput, occurs at the surface of the gas-liquid interface in thesecells. The sampled air passes through vacuum pump 24 while the liquidcan be bled off from the separator or continuously removed. No pumps arerequired, the liquid and air being transported by the single vacuum pump24 acting through the cells 14 and liquid-air separator 20 lines.

The ambient air streams passing to the cells are processed in adsorptioncolumns in order to separate the gaseous components which are measured.Five adsorbent columns 26, 28, 30, 32 and 34 are used. The nature andfunctions of these columns are indicated as follows:

Column Gaseous Outputs Nitric Oxide as Nitrogen Dioxide 26.Ascarite-Fcrrous Sulfate- Chromic Oxide The cells 14 are arranged inconjunction with a cell assembly photomultiplier as indicated at 36 andin the shown and described embodiment set up for five channels. Thiscell assembly is shown in greater detail in FIGS. 3-7 inclusive. Thestructure includes a photomultiplier tube housing assembly 38 having aphotomultiplier tube 40 mounted and contained therein with appropriateconnections including a high voltage connector 42 and a signal outconnector 44. Connected to housing 38 is a reaction cell housinggenerally designated 46 by appropriate means which mounts the variousU-shaped testing cells 14 having a configuration as shown in FIG. 4. Thereaction cell configurations are all similar in the apparatus. The cellsare mounted through radial slots 48 leading to apertures 50 in thereaction cell housing. Interconnected into a leg of each test cell is anair in tube 52 for introduction of ambient air for testing and a luminolin tube 54 and hydrogen peroxide (H 0 in tube 56 all of which enterthrough a teflon plug 58 sealing the end of the tube. The opposite endof the test cell is connected by tube 60 for exhaust. The foregoingdetails are apparent from FIG. 3 of the drawings. Interposed between thetest cells and photo-multiplier tube assembly is a neutral densityfilter generally 62 consisting of five filter segments 62A, 62B, 62C,62D and 62B supported in a filter holder 64 in conjunction with a filterretainer 66. Apertures 68 are provided in line in the filter holder andretainer to permit filter operation. Filter details are shown in FIGS.and 6. A rotary shutter 70 is rotatably mounted on a shaft in bearing 72and is provided with a shutter aperture 74 having a light sealing O-ring76 around the shutter aperture.

A drive motor 78 is provided for the rotary shutter and which preferablycan consist of a rpm synchronous, 110 V. 3.0., 60 H2, 1 42 is mounted bymotor support posts 80 of appropriate size and number. A motor couplinggenerally indicated at 82 is operatively associated with the rotaryshutter shaft. For the sequential phasing operational movement of theshutter for activating the various test cells a 110 V. ac. solenoid 84is attached by means of solenoid bracket 86 to the cell housings. A fivetoothed ratchet wheel 88 is adapted for axial movement by solenoid 84upon releasing index pawl 90 and relieving spring pressure of solenoidreturn spring 92 on shutter O-ring 76. This solenoid return spring notonly applies pressure on the shutter O-ring but also resets the indexpawl 90. The solenoid function is accomplished through a solenoid lever94 pivotably mounted on lever bracket 96 and which lever is bifurcatedat its free end 98 for engagement through pins 100 with ratchet wheel88. A pawl block 102 mounts a pawl latch 104 with operatively attachedpawl spring 106. Details of the foregoing mechanism are clearly shown inFIGS. 2 and 4 of the drawings.

The foregoing described mechanism is designed for the chemiluminescencemethod of monitoring air pollutants utilizing five microreactors(channels) simultaneously by means of sequential monitoring by a singlephoto-multiplier. The channel monitoring is controlled by the rotaryshutter which moves discretely from channel to channel and aquantitative analysis of the gaseous components of the atmosphere isobtained by comparison of the signals obtained from the separatechannels with calibrated standards for each channel. The signalprocessing may utilize a simple computer circuitry. An operating circuitis schematically depicted in FIG. 7 of the drawings. The variousstations (five in number) are indicated on FIG. 4 of the drawings andinclude:

Station 1 Filtered air (background reference) Station 2 Ozone (O Station3 Nitrogen dioxide (N0 0) Station 4 Nitric oxide and nitrogen dioxide(NO +NO) Station 5 Sulfur dioxide (S0,).

The foregoing are indicated in gaseous outputs.

Referring to FIG. 7 of the drawings operation of the photo-multipliertube 40 and shutter wheel or shutter 70 are activated from a highvoltage power supply 108 and a shutter pawl timer 110 respectively.Signals from the photo-multiplier pass through signal out lead 112 to apre-amplifier 114 and thence to integrator amplifier 116, digitalvoltmeter 118, computer 120 to printer 122 for test result indication. Alow voltage power supply 124 feeds pre-amplifier 114 and integratoramplifier 116. Timer 110 is operatively interconnected with integratoramplifier 116 through start lead 126 and reset lead 128. Timer 110 isalso operatively connected with the digital voltmeter, computer andprinter respectively through print command lead 130 stop command lead132 and start command lead 134 as schematically illustrated in FIG. 7.

The following table shows the sequence of timed events for the fivechannel system shown and described herein. In essence, each cell will beread once every minute and the integrated signal from each will be usedto calculate an analysis of each of the four gaseous constituents on theschedule, reference being made to the gaseous station details on FIG. 4.

0 Seconds Shutter Window at Station No. l g

+ 1 Seconds Start Integrator +ll Seconds Transfer Signal to Digitalvoltmeter and/or Recorder or Computer +12 Seconds Signal Off and ResetIntegrator +12 Seconds Rotate Window to Station No. 2

+13 Seconds Start Integrator +23 Seconds Transfer Signal to DigitalVoltmeter,

etc.

+24 Seconds Rotate Window to Station No. 3

+25 Seconds Start Integrator +35 Seconds Transfer Signal to DigitalVoltmeter,

etc.

+36 Seconds Rotate Window to Station No. 4

+37 Seconds Start Integrator +47 Seconds Transfer Signal to DigitalVoltmeter,

etc.

+48 Seconds Rotate Window to Station No. 5

+49 Seconds Start Integrator +59 Seconds Transfer Signal to DigitalVoltmeter,

etc.

+60 Seconds Rotate Window to Station No. l

REPEAT OPERATION Subsequent to the foregoing time sequence repeatoperation is initiated.

Operation of the invention will be more readily understood from resultsof sensitivity tests run to determine sensitivity of thechemiluminescence reaction to the four gases: S0 0 N0 and NO.

All operations were conducted dynamically. In this operation, S0 N0 andNO were diluted in two steps: l gases from tank supplies were passedinto a surge or test chamber of a six-inch pipe where they were mixedwith purified air. (2) Various quantities (50 to 1,000 ml/rnin) of thissupply were further diluted with filtered air in a second dilution step.Utilization of this two-step procedure made available dilutions upwardfrom 19 ppb by volume. Gas samples from the dilutor were fed directlyinto the chemiluminescence reactor cell where mixing with luminol andhydrogen peroxide solutions took place. Air was passed through thesample reaction tube at flow rates from 500 ml/min to 6.7 liters/min.The liquid reagents, usually 0/25 mg/ml of luminol in 0.05 N NaOH and0.6 percent 11,0 were fed to the cells. The cell was placed directlynext to the two-inch (diameter) face of an EMI (9558) photo-multipliertube which monitored the light output from the reaction. Liquid reagentswere fed into the cell at rates from 0.1 to 0.5 ml/minute each. Theoptical cell tubing diameter was 0.187 in., ID. The liquid-gas mixturewas pulled by a Neptune-Dyna pump into a separation chamber, which inthese tests was a separatory flask. The gases were then exhausted fromthe pump into the room atmosphere.

For tests with pure gas components, air was passed through charcoalfilters before use. The main supply passed through an MSA CBR 86475filter assembly before diluting the pollutant test sample. A CMACanister Air Purifier, Serial C (Bameby-Cheney Corporation), was used onthe air source to the sample gas supply.

Tests of atmospheric air were conducted by pulling air directly from theroom into the reactor cells.

Teflon tubing was used throughout.

Manifestly minor changes in details of construction can be effected inthe embodiment shown and described without departing from the spirit andscope of the invention and defined in and limited solely by the appendedclaims.

We claim:

1. A luminol-chemiluminescence type reaction air pollutants monitoringapparatus comprising:

A. a composite reaction cell assembly;

B. a plurality of separate microreactor test cells in said compositeassembly;

C. means for simultaneously introducing specimen samples of an ambientair mass into each said cell;

D. means for introducing aqueous solutions of chemical compounds whichproduce chemiluminescence light evolution during reaction with thepollutants into the air stream to each said cell;

E. selective adsorption means interposed in the air streams to each saidcell to separate different respectivegaseous components to be measured;

F. a single photomultiplier tube positioned proximate all said cells;and

G. monotoring means mounted intermediate said cell assembly and saidphoto-multiplier tube operable to sequentially discretely expose eachsaid cell to said photo-multiplier tube for discrete reception by saidphoto-multiplier tube of emitted produced light from each said cell.

2. Apparatus as in claim 1, said test cells consisting of lighttransmitting material for passage therethrough of produced light to saidphoto-multiplier tube.

3. Apparatus as in claim 2, said reaction cell assembly including ahousing body, said test cells comprising U-shaped tubes spacedly mountedin said housing, a leg of each tube being connected to the ambient airintroducing means and to the aqueous solutions introducing means.

4. Apparatus as in claim 3, said test cells being five in number andspacedly arranged in said housing, said selective adsorption meanscomprising columns equal in number to said cells and respectivelycontaining ascarite-ferrous sulfate-chromic oxide, ferroussulfatechromic oxide, chromic oxide, ferrous sulfate and charcoalrespectively operable to produce gaseous outputs of nitrogen dioxide,nitric oxide and nitrogen dioxide, ozone, sulfur dioxide, and filteredair for background samples.

5. Apparatus as in claim 4, including a multi segment neutral densityfilter interposed between said cell assembly and said photo-multipliertube, the filter segments being operable to extend the sensitivity rangeof a photo-multiplier sensor detecting emitted light from said cells.

6. Apparatus as in claim 5, said means to sequentially expose each saidcell comprising a rotary shutter having an aperture, said rotary shutterbeing rotatably mounted, drive means for said rotary shutter, and meansfor sequential phasing operational movement of the shutter foractivating sequentially said test cells for light transmission to saidphoto-multiplier tube.

7. Apparatus as in claim 6, and including a five toothed ratchet wheeland a release index pawl for controlled movement of said ratchet wheel,said ratchet wheel being connected to said shutter and operable forsequential rotational movement thereof to position said aperture at asaid test cell in open communication with said photo-multiplier tube.

8. Apparatus as in claim 7 and including means for sequentiallyoperatively engaging said ratchet wheel and said shutter permittingrotation of said shutter.

9. Apparatus as in claim 3 and including an exhaust liquid-gas separatorfrom said cells connected to the other of the legs of said U-shapedtubes and a single vacuum pump for transporting liquid and air throughthe exhaust, sampled air passing through said vacuum pump and liquidbeing separated therefrom.

10. Apparatus as in claim 4 and test signal readout means for receivingand correlating signals from said photo-multiplier tube for each saidcell discretely for quantitative analysis of specific pollutantscontained in air samples introduced into said test cells.

11. A luminol-chemiluminescence type reaction air pollutants monitoringapparatus comprising:

A. a composite reaction cell assembly;

B. five discrete test cells spacedly arranged in said assembly;

C. said test cells consisting of U-shaped tubes of light transmittingmaterial;

D. means for simultaneously introducing samples of ambient air into aleg of each cell tube;

E. means for introducing aqueous solutions of chemical compounds whichproduce chemiluminescence light evolution during reaction withpollutants into the leg of the tube of each said cell having the airstream introduced therein;

F. selective adsorption means interposed in the air streams to each saidcell to separate gaseous components to be measured, and including:

i. columns equal in number to said cells and respectively containingascarite-ferrous sulfatechromic oxide, ferrous-sulfate-chromic oxide,chromic oxide, ferrous sulfate and charcoal respectively operable toproduce gaseous outputs of nitrogen dioxide, nitric oxide and nitrogendioxide, ozone, sulfur dioxide, and filtered air for background samples;

G. a photo-multiplier tube positioned proximate all said cells; and

H. means mounted intermediate said cell assembly and saidphoto-multiplier tube operable to sequentially discretely expose eachsaid cell to said photd multiplier tube for discrete reception ofemitted produced light from each said cell.

12. Apparatus as in claim 11, including a multi segment neutral densityfilter interposed between said cell assembly and said photo-multipliertube, the filter segments being operable to extend the sensitivity rangeof a photo-multiplier sensor detecting emitted light from said cells.

13. Apparatus as in claim 12, said means to sequentially expose eachsaid cell comprising a rotary shutter having an aperture, said rotaryshutter being rotatably mounted, drive means for said rotary shutter,and means for sequential phasing operational movement of the shutter foractivating sequentially said test cells for light transmission to saidphoto-multiplier tube.

14. Apparatus as in claim 13, and including a five toothed ratchet wheeland a release index pawl for controlled movement of said ratchet wheel,said ratchet wheel being connected to said shutter and operable forsequential rotational movement thereof to position said aperture at asaid test cell in open communication with said photo-multiplier tube.

15. Apparatus as in claim 14, and including means for sequentiallyoperatively engaging said ratchet wheel and said shutter permittingrotation of said shutter.

16. Apparatus as in claim 11 and including an exhaust liquid-gasseparator from said cells connected to the other of the legs of saidU-shaped tubes'and a single vacuum pump for transporting liquid and airthrough the exhaust, sampled air passing through said vacuum pump andliquid being separated therefrom.

17. Apparatus as in claim 11 and test signal readout means for receivingand correlating signals from said photo-multiplier tube for each saidcell discretely for quantitative analysis of specific pollutantscontained in air samples introduced into said test cells.

a a a: r s

1. A luminol-chemiluminescence type reaction air pollutants monitoringapparatus comprising: A. a composite reaction cell assembly; B. aplurality of separate microreactor test cells in said compositeassembly; C. means for simultaneously introducing specimen samples of anambient air mass into each said cell; D. means for introducing aqueoussolutions of chemical compounds which produce chemiluminescence lightevolution during reaction with the pollutants into the air stream toeach said cell; E. selective adsorption means interposed in the airstreams to each said cEll to separate different respective gaseouscomponents to be measured; F. a single photo-multiplier tube positionedproximate all said cells; and G. monotoring means mounted intermediatesaid cell assembly and said photo-multiplier tube operable tosequentially discretely expose each said cell to said photo-multipliertube for discrete reception by said photo-multiplier tube of emittedproduced light from each said cell.
 2. Apparatus as in claim 1, saidtest cells consisting of light transmitting material for passagetherethrough of produced light to said photo-multiplier tube. 3.Apparatus as in claim 2, said reaction cell assembly including a housingbody, said test cells comprising U-shaped tubes spacedly mounted in saidhousing, a leg of each tube being connected to the ambient airintroducing means and to the aqueous solutions introducing means. 4.Apparatus as in claim 3, said test cells being five in number andspacedly arranged in said housing, said selective adsorption meanscomprising columns equal in number to said cells and respectivelycontaining ascarite-ferrous sulfate-chromic oxide, ferroussulfate-chromic oxide, chromic oxide, ferrous sulfate and charcoalrespectively operable to produce gaseous outputs of nitrogen dioxide,nitric oxide and nitrogen dioxide, ozone, sulfur dioxide, and filteredair for background samples.
 5. Apparatus as in claim 4, including amulti segment neutral density filter interposed between said cellassembly and said photo-multiplier tube, the filter segments beingoperable to extend the sensitivity range of a photo-multiplier sensordetecting emitted light from said cells.
 6. Apparatus as in claim 5,said means to sequentially expose each said cell comprising a rotaryshutter having an aperture, said rotary shutter being rotatably mounted,drive means for said rotary shutter, and means for sequential phasingoperational movement of the shutter for activating sequentially saidtest cells for light transmission to said photo-multiplier tube. 7.Apparatus as in claim 6, and including a five toothed ratchet wheel anda release index pawl for controlled movement of said ratchet wheel, saidratchet wheel being connected to said shutter and operable forsequential rotational movement thereof to position said aperture at asaid test cell in open communication with said photo-multiplier tube. 8.Apparatus as in claim 7 and including means for sequentially operativelyengaging said ratchet wheel and said shutter permitting rotation of saidshutter.
 9. Apparatus as in claim 3 and including an exhaust liquid-gasseparator from said cells connected to the other of the legs of saidU-shaped tubes and a single vacuum pump for transporting liquid and airthrough the exhaust, sampled air passing through said vacuum pump andliquid being separated therefrom.
 10. Apparatus as in claim 4 and testsignal readout means for receiving and correlating signals from saidphoto-multiplier tube for each said cell discretely for quantitativeanalysis of specific pollutants contained in air samples introduced intosaid test cells.
 11. A luminol-chemiluminescence type reaction airpollutants monitoring apparatus comprising: A. a composite reaction cellassembly; B. five discrete test cells spacedly arranged in saidassembly; C. said test cells consisting of U-shaped tubes of lighttransmitting material; D. means for simultaneously introducing samplesof ambient air into a leg of each cell tube; E. means for introducingaqueous solutions of chemical compounds which produce chemiluminescencelight evolution during reaction with pollutants into the leg of the tubeof each said cell having the air stream introduced therein; F. selectiveadsorption means interposed in the air streams to each said cell toseparate gaseous components to be measured, and including: i. columnsequal in number to said cells and respectively containingascarite-ferrous sulfate-chrOmic oxide, ferrous-sulfate-chromic oxide,chromic oxide, ferrous sulfate and charcoal respectively operable toproduce gaseous outputs of nitrogen dioxide, nitric oxide and nitrogendioxide, ozone, sulfur dioxide, and filtered air for background samples;G. a photo-multiplier tube positioned proximate all said cells; and H.means mounted intermediate said cell assembly and said photo-multipliertube operable to sequentially discretely expose each said cell to saidphoto-multiplier tube for discrete reception of emitted produced lightfrom each said cell.
 12. Apparatus as in claim 11, including a multisegment neutral density filter interposed between said cell assembly andsaid photo-multiplier tube, the filter segments being operable to extendthe sensitivity range of a photo-multiplier sensor detecting emittedlight from said cells.
 13. Apparatus as in claim 12, said means tosequentially expose each said cell comprising a rotary shutter having anaperture, said rotary shutter being rotatably mounted, drive means forsaid rotary shutter, and means for sequential phasing operationalmovement of the shutter for activating sequentially said test cells forlight transmission to said photo-multiplier tube.
 14. Apparatus as inclaim 13, and including a five toothed ratchet wheel and a release indexpawl for controlled movement of said ratchet wheel, said ratchet wheelbeing connected to said shutter and operable for sequential rotationalmovement thereof to position said aperture at a said test cell in opencommunication with said photo-multiplier tube.
 15. Apparatus as in claim14, and including means for sequentially operatively engaging saidratchet wheel and said shutter permitting rotation of said shutter. 16.Apparatus as in claim 11 and including an exhaust liquid-gas separatorfrom said cells connected to the other of the legs of said U-shapedtubes and a single vacuum pump for transporting liquid and air throughthe exhaust, sampled air passing through said vacuum pump and liquidbeing separated therefrom.
 17. Apparatus as in claim 11 and test signalreadout means for receiving and correlating signals from saidphoto-multiplier tube for each said cell discretely for quantitativeanalysis of specific pollutants contained in air samples introduced intosaid test cells.